arch/arm/boot/dts/sun4i-a10.dtsi: convert to the new RTC compatibles

Switch the device tree to the new compatibles introduced in the RTC
drivers to have a common pattern accross all Allwinner SoCs.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>